Having developed a non-invasive technique using I-131 hippurate for measuring relative renal blood flow in dogs using the scintillation camera interfaced to a minicomputer, we are now applying the technique to several clinical problems. These include the comparison of the radioisotope study with the rapid sequence intravenous pyelogram for predicting the results of renal arteriography and renal vein renin ratios in hypertensive patients, measurement of relative renal blood flow pre and post operatively in patients undergoing renal-splenic shunting for portal hypertension. BIBLIOGRAPHIC REFERENCES: Shames, DM and Korobkin, M. "A simple technique for measuring relative renal blood flow". J. Nucl. Med. 17:876, 1976.